whichlib
The dependency picker for coding agents. Ask which library to use and get a
scored, verified answer instead of a guess.
whichlib is an MCP server with three tools. It speaks MCP 2026-07-28;
older clients keep working. Every repository it returns
carries a transparent 0–100 score (momentum, maintenance, adoption including
npm and PyPI downloads, license), a tier, a one-line verdict and the full
breakdown, so the agent can justify the pick and you can read why.
For teams (waitlist): alerts when a dependency your repos use goes stale,
and rules your team's coding agents must follow when they add one. Add a 👍
to the waitlist issue; at 20
signups it gets built. whichlib itself stays free.
Install
Claude Code:
Cursor, Windsurf and other MCP clients:
Requires Node 22 or newer. No account, no API key.
Use it without installing (hosted, no Node needed):
Limits and the web API: https://whichlib.com/docs/
Tools
Example, in Claude Code: "which Python PDF parser should I use?" →
MinerU, pdfplumber, pypdf with scores, weekly downloads and verdicts like
"Rising fast, 26k downloads/wk, pushed 3 days ago, Apache-2.0".
Score
Tiers: Strong ≥ 75, Solid ≥ 50, Watch ≥ 25, Avoid; repos younger than 30
days are New ("Too new to judge"), whatever their score. Archived repos are
capped at 20. On a 20-need eval the top recommendation is an accepted answer 75% of
the time and the top five contain one 100% of the time; the eval and its
reports live in the repository.
Environment variables, all optional
GITHUB_TOKEN: raises GitHub's search limit from 10 to 30 per minute. A
fine-grained token with no permissions is enough. Recommend makes three
searches per call.
WHICHLIB_HISTORY=off: do not download daily star counts. By default the
server keeps the last 10 days in ~/.whichlib/stars/, refreshed in the
background at most every 12 hours from raw.githubusercontent.com, so
momentum uses real stars gained per week for the top 1,000 repos per
language and new trending repos. Nothing is sent with that download.
FRESH_REPOS_DATA_DIR: a folder of daily snapshots or star counts to use
instead (see the repository's data branch).
WHICHLIB_TELEMETRY=off or DO_NOT_TRACK=1: disables anonymous call
counting. What is counted: tool name, a random install id, version,
platform, Node major version, the MCP protocol version of the call. Never queries, repository names or results.
The aggregate numbers are public at
https://whichlib-telemetry.todorovskijosif.workers.dev/stats.
Source, dashboard, data
Repository: https://github.com/josifb/whichlib (MIT). It also holds the
Fresh Repos dashboard (most-starred new repositories, day / week / month,
sortable, one HTML file), the nightly snapshot and enrichment jobs, the
recommendation eval, and 80+ unit tests.
Development, from the whichlib/ folder of the repository:
Layout: